This prospective cohort study examines the role of prenatal and early postnatal lead exposure on the neuropsychological status and social adjustment of adolescents enrolled in the Cincinnati Lead Study. We are examining the relationship between moderate exposure to lead and neuropsychological deficits, difficulties in peer relationships, personality disturbances and juvenile delinquency. This birth cohort of approximately 300 subjects has been followed since 1980 with regularly scheduled assessments of blood lead concentrations, health history, social and hereditary factors, and neurobehavioral development.